scholarly journals Energy and exergy analysis and optimum working conditions of a renewable energy system using a transient systems simulation program

2020 ◽  
Vol 38 (4) ◽  
pp. 1248-1261
Author(s):  
Nidal H Abu-Hamdeh ◽  
Khalid A Alnefaie
Keyword(s):  
Electrical Power ◽  
Energy System ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Cooling Power ◽  
Single Family ◽  
Generation System ◽  
Absorption Chiller ◽  
Domestic Hot Water ◽  
Energy And Exergy

A solar tri-generation system comprises of photovoltaic thermal collectors that are used for the production of electrical power and domestic hot water simultaneously. This study presents the performance analysis of a micro-solar tri-generation system that fulfills the requirements of an off-grid single-family lodging. The main functions of this system include domestic hot water, electrical power, and cooling power production. A set of five photovoltaic thermal panels were modeled together. The electrical power generated was stored in a battery, while the hot water generated was passed through a flow diverting valve. This valve directed some of the hot water to an absorption chiller, while the remaining portion was sent to an insulated thermal storage tank for later use. Energy and exergy analyses were performed to evaluate the extracted energy’s quality and efficiency. The overall thermal energy efficiency achieved was 50.53%. The extracted energy in the form of hot water was 3777.5 W. The electrical power generated was 2984.6 W, which was sufficient for the small single-family lodging. The coefficient of performance of the absorption chiller was found to be 0.6152. The exergy efficiency achieved was 36.88%. The exergy extracted by hot water was 234.3 W, while the electrical exergy generated was 2984.6 W. The exergy extracted during refrigeration was found to be 91.22 W. Furthermore, varying wind speeds and tilt angles affected both the energy and exergy efficiencies. The tilt angle must be kept at less than 45°, and the optimum wind speed was determined to be 35 km/h.

scholarly journals Experimental and Theoretical Study of the Energy Flow of a Two Stages Four Generators Adsorption Chiller

2019 ◽  
Vol 14 (2) ◽  
pp. 129-136
Author(s):  
Faeza Mahdi Hadi
Keyword(s):  
Activated Carbon ◽  
Cold Water ◽  
Water Cycle ◽  
Electrical Power ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Cooling Power ◽  
Low Grade ◽  
Adsorption Chiller ◽  
Two Stages

This work is concerned with a two stages four beds adsorption chiller utilizing activated carbon-methanol adsorption pair that operates on six separated processes. The four beds that act as thermal compressors are powered by a low grade thermal energy in the form of hot water at a temperature range of 65 to 83 °C.  As well as, the water pumps and control cycle consume insignificant electrical power. This adsorption chiller consists of three water cycles. The first water cycle is the driven hot water cycle. The second cycle is the cold water cycle to cool the carbon, which adsorbs the methanol. Finally, the chilled water cycle that is used to overcome the building load. The theoretical results showed that average cycle cooling power is 2.15kW, while the experimental measurement revealed that the cooling capacity of the cycle is about 1.98 kW with a relative error of % 0.02. The generator and condensing temperatures are 83 and 30 °C, respectively. The coefficient of performance (COP) of that chiller was in the range of 0.37 to 0.49. The best operating point and the best working conditions were also investigated. The present chiller is superior more than the single stage, two beds adsorption chiller that works on the activated carbon methanol pair that needs a high ambient temperature.

scholarly journals Energy and Exergy Analysis of the Air Source Transcritical CO2 Heat Pump Water Heater Using CO2-Based Mixture as Working Fluid

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4470
Author(s):  
Yikai Wang ◽  
Yifan He ◽  
Yulong Song ◽  
Xiang Yin ◽  
Feng Cao ◽  
...  
Keyword(s):  
Exergy Analysis ◽  
Heat Pumps ◽  
Exergy Efficiency ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Domestic Hot Water ◽  
Practical Applications ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis

Given the large demand nowadays for domestic hot water, and its impact on modern building energy consumption, air source transcritical CO2 heat pumps have been extensively adopted for hot water production. Since their system efficiency is limited by significant irreversibility, a CO2-based mixture could offer a promising drop-in technology to overcome this deficiency without increasing system complexity. Although many CO2 blends have been studied in previously published literature, little has been presented about the CO2/R32 mixture. Therefore, a proposed mixture for use in transcritical CO2 heat pumps was analyzed using energy and exergy analysis. Results showed that the coefficient of performance and exergy efficiency variation displayed an “M” shape trend, and the optimal CO2/R32 mixture concentration was determined as 0.9/0.1 with regard to flammability and efficiency. The irreversibility of the throttling valve was reduced from 0.031 to 0.009 kW⋅kW−1 and the total irreversibility reduction was more notable with ambient temperature variation. A case study was also conducted to examine domestic hot water demand during the year. Pure CO2 and the proposed CO2 blend were compared with regard to annual performance factor and annual exergy efficiency, and the findings could provide guidance for practical applications in the future.

scholarly journals Seasonal Energy Flexibility Through Integration of Liquid Sorption Storage in Buildings

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2944
Author(s):  
Luca Baldini ◽  
Benjamin Fumey
Keyword(s):  
Energy Storage ◽  
Heat Pump ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Energy System ◽  
Coefficient Of Performance ◽  
Electric Load ◽  
Single Family ◽  
Electricity Grid

The article estimates energy flexibility provided to the electricity grid by integration of long-term thermal energy storage in buildings. To this end, a liquid sorption storage combined with a compression heat pump is studied for a single-family home. This combination acts as a double-stage heat pump comprised of a thermal and an electrical stage. It lowers the temperature lift to be overcome by the electrical heat pump and thus increases its coefficient of performance. A simplified model is used to quantify seasonal energy flexibility by means of electric load shifting evaluated with a monthly resolution. Results are presented for unlimited and limited storage capacity leading to a total seasonal electric load shift of 631.8 kWh/a and 181.7 kWh/a, respectively. This shift, referred to as virtual battery effect, provided through long-term thermal energy storage is large compared to typical electric battery capacities installed in buildings. This highlights the significance of building-integrated long-term thermal energy storage for provision of energy flexibility to the electricity grid and hence for the integration of renewables in our energy system.

scholarly journals Installation and Operation of a Solar Cooling and Heating System Incorporated with Air-Source Heat Pumps

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 996 ◽  
Author(s):  
Li Huang ◽  
Rongyue Zheng ◽  
Udo Piontek
Keyword(s):  
Heating System ◽  
Cooling Capacity ◽  
Heat Pumps ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Energy Yield ◽  
Absorption Chiller ◽  
Annual Average ◽  
Water Storage Tank ◽  
Solar Cooling

A solar cooling and heating system incorporated with two air-source heat pumps was installed in Ningbo City, China and has been operating since 2018. It is composed of 40 evacuated tube modules with a total aperture area of 120 m2, a single-stage and LiBr–water-based absorption chiller with a cooling capacity of 35 kW, a cooling tower, a hot water storage tank, a buffer tank, and two air-source heat pumps, each with a rated cooling capacity of 23.8 kW and heating capacity of 33 kW as the auxiliary system. This paper presents the operational results and performance evaluation of the system during the summer cooling and winter heatingperiod, as well as on a typical summer day in 2018. It was found that the collector field yield and cooling energy yield increased by more than 40% when the solar cooling and heating system is incorporated with heat pumps. The annual average collector efficiency was 44% for cooling and 42% for heating, and the average coefficient of performance (COP) of the absorption chiller ranged between 0.68 and 0.76. The annual average solar fraction reached 56.6% for cooling and 62.5% for heating respectively. The yearly electricity savings accounted for 41.1% of the total electricity consumption for building cooling and heating.

scholarly journals Analysis of energy signatures and planning of heating and domestic hot water energy use in buildings in Norway

2019 ◽  
Vol 111 ◽  
pp. 06009
Author(s):  
Tymofii Tereshchenko, ◽  
Dmytro Ivanko ◽  
Natasa Nord ◽  
Igor Sartori
Keyword(s):  
Energy Use ◽  
District Heating ◽  
Energy System ◽  
Energy Performance ◽  
Multiple Regression Model ◽  
Hot Water ◽  
Temperature Dependent ◽  
Domestic Hot Water ◽  
Dependent Part ◽  
Energy Signature

Widespread introduction of low energy buildings (LEBs), passive houses, and zero emission buildings (ZEBs) are national target in Norway. In order to achieve better energy performance in these types of buildings and successfully integrate them in energy system, reliable planning and prediction techniques for heat energy use are required. However, the issue of energy planning in LEBs currently remains challenging for district heating companies. This article proposed an improved methodology for planning and analysis of domestic hot water and heating energy use in LEBs based on energy signature method. The methodology was tested on a passive school in Oslo, Norway. In order to divide energy signature curve on temperature dependent and independent parts, it was proposed to use piecewise regression. Each of these parts were analyzed separately. The problem of dealing with outliers and selection of the factors that had impact of energy was considered. For temperature dependent part, the different methods of modelling were compared by statistical criteria. The investigation showed that linear multiple regression model resulted in better accuracy in the prediction than SVM, PLS, and LASSO models. In order to explain temperature independent part of energy signature the hourly profiles of energy use were developed.

scholarly journals Investigation of temperature drop in domestic hot water circuit

2018 ◽  
Vol 44 ◽  
pp. 00158
Author(s):  
Ilona Rzeźnik
Keyword(s):  
Experimental Investigation ◽  
Energy Savings ◽  
Temperature Drop ◽  
Pump Energy ◽  
Working Time ◽  
Hot Water ◽  
Single Family ◽  
Domestic Hot Water ◽  
Circulation Pump ◽  
Family House

The results of experimental investigation of determining the time of temperature drop in domestic hot water circuit were presented in this paper on the example of single-family house. The test were carried out on vertical sections of installations made of PE-X/Al/PE pipes (cross-linked polyethylene and aluminum) with and without insulation. The temperature drop process was investigated in temperature range typical for domestic hot water installation from 55ºC to 40ºC. On the basis of the obtained results with appropriate adjustment of the working time of circulation pump, energy savings of 90% were achieved.

The Energy and Exergy Efficiencies of Renewable Energy Utilization in a Building Stock

2013 ◽  
Vol 361-363 ◽  
pp. 335-338
Author(s):  
Xiao Chen
Keyword(s):  
Renewable Energy ◽  
Exergy Analysis ◽  
Hot Water ◽  
Energy Utilization ◽  
Efficiency Improvement ◽  
Building Stock ◽  
Domestic Hot Water ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Heating Mode

An surface water heat pump (SWHP) system and some solar domestic hot water (SDHW) systems were constructed in a building stock located in Xiangtan for the purpose of energy saving and environmental improvement. This study aims to evaluate the energy and exergy efficiencies of renewable energy utilization based on energy and exergy analysis. We found the energy and exergy efficiencies of the SWHP system in heating mode to be 395% and 17.78%, respectively. The energy and exergy efficiencies for the SDHW systems were found to be 34.96% and 17.5%, respectively. Some measures for the exergy efficiency improvement are discussed in this paper.

scholarly journals Desalination of Agricultural Wastewater by Solar Adsorption System: A Numerical Study

2021 ◽  
Vol 10 (4) ◽  
pp. 901-910
Author(s):  
Jehan F AlRubaiea ◽  
Farkad A Latteiff ◽  
Jasim M Mahdi ◽  
Mohammed A Atiya ◽  
Hasan Sh Majdi
Keyword(s):  
Silica Gel ◽  
Numerical Study ◽  
High Energy ◽  
Water Desalination ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Cooling Power ◽  
Adsorption System ◽  
Factors Affecting ◽  
Usage Cost

There are still areas around the world suffer from severe shortage of freshwater supplies. Desalination technologies are not widely used due to their high energy usage, cost, and environmental damaging effects. In this study, a mathematical model of single-bed adsorption desalination system using silica gel-water as working pair is developed and validated via earlier experiments. A very good match between the model predictions and the experimental results is recorded. The objective is to reveal the factors affecting the productivity of fresh water and cooling effect in the solar adsorption system. The proposed model is setup for solving within the commercially-available software (Engineering Equation Solver). It is implemented to solve the mass and heat balance equations for the adsorbent bed, condenser, and evaporator components. At a typical temperature of 89 °C and flow rate of 30 m3/sec for the hot water entering the bed, the following results are reported: (a) the specific daily water production of 1.89 m3 /ton of silica gel/ day, (b) coefficient of performance of 0.32, and (c) specific cooling power of 40.82 W/kg of silica gel. The concentration of salt (X) in the product (desalinated water) has been set with value of 0.5 gm/kg to be suitable for drinking and irrigation. The salt concentration in the evaporator is estimated to be 4.611 gm/kg during the overall adsorption process. The results from this study should be of wide interest for the field of solar water desalination and air-conditioning.

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